Can an LPN function as an RT?

I was wondering if anyone knew the answer to this question? I am taking my health science pre-reqs at a community college, and I recently heard a student saying she heard the hospitals/home health agencies used to allow the LPNs to perform RT duties. I was wondering if anyone knew if this was a valid statement or not?
I am a college freshman with a 3.4 GPA. I have already taken Anatomy/Physiology I & II, English, Med. Terminology, and Psychology. However, I am having a really tough time deciding on whether to major in respiratory care or nursing. I think my problem is I find all aspects of the medical field very interesting! (I started out as a surgical tech major, but I job shadowed last semester a few times and decided it was not for me.)